In the movement of an intermediate length of a web material such as might be found in the textile industry, the web oftentimes passes through a plurality of separate or related operations in an overall process. In each of these operations it is desirable and sometimes essential that the web be in a particular position with respect to the apparatus to ensure proper processing of the web without causing damage to the web or producing "off quality" goods. Since, as a general rule, the apparatus handling the web is substantially wider than the width of the web, lateral movement of the web across the apparatus is probable. Such lateral movement can create improper web alignment with respect to the particular equipment. Proper web alignment is particularly important in those processes where the web needs to be brought into registry to permit a normal process function. For example, in laminating, printing, tentering, and similar operations, a web must first be properly aligned prior to commencing of the process. Likewise, through not necessarily essential, good web alignment is greatly preferred for batching, coating, and virtually all web handling processes. Movement of the web out of the anticipated path of web travel may subject the web to unused and soiled parts of the web handling equipment.
Certain webs also tend to curl or roll up along the edges during handling. During winding of a web with a curled edge, an unsightly and technically poor package will be produced. In those operations where the attitude of the web is critical, such as bonding, printing and the like, it is essential that any curl, creases, folds and the like be removed. Uncurling devices are then often needed to remove curl from the selvages of the web. Numerous uncurling devices have been developed heretofore, the majority of which have some attendant disadvantages.
Several techniques have heretofore been developed to control the lateral position of a moving web. Each of these techniques employs a device to detect the position of the web and to actuate a correctional means responsive thereto. Oftentimes these detectors include a beam of light that is directed across a predetermined area with a photo receiver being positioned on the opposite side of the web path. Once the web breaks the beam of light, or permits the light to be received by the photo conductor, as the system dictates, certain means are actuated to signal that the web is out of proper alignment. The web can then be manually or automatically adjusted to its proper path of travel to provide for further proper processing thereof.
The present invention represents an improvement in the art of such devices as will be described in complete detail hereinafter. There is no known prior art that would anticipate or suggest the method or apparatus of the present invention.